1. Field of the Invention
The present invention relates to a switching device of networks-on-chip system, and a scheduling method thereof. More specifically, the present invention relates to a switching device of a networks-on-chip system and a scheduling method thereof, which is capable of variably allocating codes in accordance with the number of ports actually possessing data.
2. Description of the Related Art
Following the convergence of the fields of computers, communications and broadcasting, demands are rapidly changing from the ASIC (Application Specific IC) and ASSP (Application Specific Standard Product) to SoC (System on Chip). In addition to this, compactness and simplification and high functionality of IT (Information Technology) devices also stimulate SoC industry.
SoC is a technology-integrated semiconductor technique which realizes complicated systems of different functions into a single chip. Many studies are conducted for realization of SoC, and above all, a way to connect different ID elements built in the chip to each other, has been considered the most important issue.
A bus-based connection is widely used to connect IP elements. However, as the chip density increases and amount of information flow between IP elements surges, bus-based SoC has almost reached its structural limit.
In an attempt to overcome the above-mentioned problems of the bus-based SoC structure, a NoC (networks-on-chip), which incorporates general network technology in chips to connect IPs, has been newly suggested.
Active studies are being conducted by many laboratories around the world, and currently developing NoC architectures include, according to the type of switching, TDMA (Time Division Multiple Access)-based NoC, and CDMA (Code Division Multiple Access)-based NoC.
CDMA-based NoC uses orthogonality of the codes, and thus is capable of using wide bandwidth and robust to noise. However, a scheduling technology to guarantee switch fairness and prevent starvation of the NoC switch, has yet to be developed.
The CDMA switch also has a problem of occupying wide bandwidth even when there is a relatively few number of IPs to send signals from one point, because the fixed code length is used according to the conventional way.
FIG. 1 shows the structure of a conventional CDMA switch.
In CDMA switch, generally at least two IPs share one common switch. The CDMA switch of FIG. 1 illustrates the example where eight IPs A to H share one single switch.
In order to perform switching of eight IPs A to H in a star structure, it is always required to assign eight bits of different Walsh codes to the respective IPs. The following table 1 shows the Walsh Codes which are differently assigned to each of the IPs A to H.
TABLE 1Resource AddressAssigned CodeA00000000B01010101C00110011H01101001
As shown above, different codes are required for each of the ports in order to perform switching of packets at the ports. Accordingly, codes are unnecessarily waste especially when only a few number of IPs intend to transmit and receive data. Additionally, the CDMA switch also requires to longer length of codes as the number of ports increase. Therefore, requirements for computations and power increase in the switch.
Furthermore, in the event of competition in the CDMA switch, there is no specific scheduling method provided to solve such a problem. As mentioned above, the scheduling is very essential for the optimum networking of a single chip such as maintaining fairness of switch and reduction of latency.
However, due to the problems as mentioned above, the CDMA switch, is not widely used despite of its various advantages. As a result, improvement is required.